chore(bench): extend pcap to install phase + utoo-next baseline

[elrrrrrrr]

What

The pcap-only bench was previously a one-off that captured p1_resolve across utoo and bun, and assumed the project was already cloned by pm-bench-phases.sh. Install-phase regressions (#2902 / #2903 / #2904 / #2905 σ widening on p0_full_cold) live in the tarball download path — not in resolve.

This PR makes the pcap bench self-contained and covers both phases for three PMs.

Script changes (bench/pm-bench-pcap.sh)

• Self-clone the project if \$PROJECT_DIR is missing (mirrors pm-bench-phases.sh)
• Add a <pm>-install capture per PM: lock pre-existing, cache + node_modules wiped, then <pm> install. This is the cold-tarball-download phase where the σ-widening lives.
• Add utoo-next as a third PM, gated on \$UTOO_NEXT_BIN so local runs still work without it.

Workflow changes (.github/workflows/pm-e2e-bench.yml)

• pm-bench-pcap-linux now downloads the utoo-next-linux-x64 artifact and exports UTOO_NEXT_BIN, exactly like bench-phases-linux does.
• The Build next branch utoo and Upload utoo-next binary steps in build-linux now also fire for inputs.target == 'pm-bench-pcap', not only pm-bench-phases.

Outputs

```
/tmp/pm-bench-pcap/
dns.txt
utoo-{resolve,install}.{pcap,log}
utoo-next-{resolve,install}.{pcap,log} (when UTOO_NEXT_BIN set)
bun-{resolve,install}.{pcap,log}
```

Why

Drives the analysis of whether the install hot-path's increased concurrency (FuturesUnordered streaming, zero-copy tar, TTY-gate) saturates outbound TCP and starves the download path — the suspect mechanism for σ widening on p0_full_cold across the #2903 / #2904 / #2905 split experiments.

Smoke test

Dispatched on this chore branch first: utoo binary and utoo-next binary built off the same code (just bench scripts differ), so any utoo-vs-utoo-next install-phase delta on this run is pure environment noise — establishes the floor before we run on the experiment branches.

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request refactors the bench/pm-bench-pcap.sh script to support capturing network traces for both the resolve and install phases across different package managers, including a new baseline option for utoo-next. It introduces a run_pm_phases function to manage the lifecycle of these phases and ensures a cold environment by clearing caches. The review feedback recommends using Bash arrays to store common command-line arguments for bun and utoo to improve maintainability and reduce duplication.

[gemini-code-assist]

The --registry argument and the BUN_INSTALL_CACHE_DIR environment variable prefix are duplicated for the bun commands. To improve maintainability and reduce redundancy, you could extract the common argument into an array. This will make future changes to arguments easier.

Suggested change

	BUN_INSTALL_CACHE_DIR="$cache_dir" \
	capture_one "${pm_name}-resolve" \
	"$pm_bin" install --lockfile-only --registry="$REGISTRY"
	rm -rf "$cache_dir" node_modules
	BUN_INSTALL_CACHE_DIR="$cache_dir" \
	capture_one "${pm_name}-install" \
	"$pm_bin" install --registry="$REGISTRY"
	local bun_args=(--registry="$REGISTRY")
	BUN_INSTALL_CACHE_DIR="$cache_dir" \
	capture_one "${pm_name}-resolve" \
	"$pm_bin" install --lockfile-only "${bun_args[@]}"
	rm -rf "$cache_dir" node_modules
	BUN_INSTALL_CACHE_DIR="$cache_dir" \
	capture_one "${pm_name}-install" \
	"$pm_bin" install "${bun_args[@]}"

[gemini-code-assist]

The arguments --registry and --cache-dir are duplicated across the utoo commands. You can extract these common arguments into an array to improve maintainability and reduce redundancy. This makes it easier to modify arguments in the future.

Suggested change

	capture_one "${pm_name}-resolve" \
	"$pm_bin" deps --registry="$REGISTRY" --cache-dir="$cache_dir"
	rm -rf "$cache_dir" node_modules
	capture_one "${pm_name}-install" \
	"$pm_bin" install --registry="$REGISTRY" --cache-dir="$cache_dir"
	local utoo_args=(--registry="$REGISTRY" --cache-dir="$cache_dir")
	capture_one "${pm_name}-resolve" \
	"$pm_bin" deps "${utoo_args[@]}"
	rm -rf "$cache_dir" node_modules
	capture_one "${pm_name}-install" \
	"$pm_bin" install "${utoo_args[@]}"

[elrrrrrrr]

pcap tooling rolled into #2924 stack (ci(pcap): install/preload/manifest captures). Archived.